This is about some of the Great Salt Lake's geology history. A long time ago there was a lake in Utah called Lake Bonneville (bon-u-vil). You can see the blue Great Salt Lake in the picture. See if you can see the flat areas on the left. This is about where Lake Bonneville was.

Lake Bonneville was very big. It covered a lot of Utah! It was about 1000 feet deep too! It did not have much salt in it. You can see where the lake was today by the flat areas on the sides of the mountains around the Salt Lake Valley. About 14 or 15 thousand years ago, there was a big flood of the lake by Idaho. A lot of the water went into the Snake River by there. The weather got hotter too. More water was going out than coming into Lake Bonneville. It got smaller and smaller and now we have the Great Salt Lake and some other lakes that are left.

Because so much water came out than came into the Lake, a lot of salt was left over. That is why the Great Salt Lake is so salty and why we have the big salt flat areas past the Great Salt Lake.

Look at the picture again. Look at the flat area again. Do you see the mountains that look like caterpillars and the flat areas in between them? These are called basins (the flat areas) and ranges (mountains). In most areas the water from the rivers and streams goes to the ocean, but in the basins and ranges area, it goes to the Great Salt Lake. So no water goes out of the Great Salt Lake. The stuff that the rivers and streams carry to the Great Salt Lake is not carried anywhere else. When the water evaporates, it leaves behind different salts and other things. This is what makes the Great Salt Lake so salty.

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